1. Field of the Invention
The present invention generally relates to computer apparatus, and more particularly relates to the dissipation of heat generated by a PCMCIA card installed in a portable computer, such as a notebook computer, or other types of computers such as desktop computers.
2. Description of Related Art
Computer expansion cards produced under the auspices of the Personal Computer Memory Cards International Association are commonly referred to as "PCMCIA" cards and can greatly expand the performance of personal computers in ways that permit users to customize their computing ability, thereby increasing the flexibility and range of capabilities of personal computers. PCMCIA cards are especially targeted toward small, highly portable computers of the types commonly known as "laptops", "notebooks" and "sub-notebooks", and can provide expanded memory, fax, modem, network and various other expansion features for their associated computers.
A typical PCMCIA card is approximately 2" wide by 3" long and consists of a printed circuit board bearing a number of electronic and semiconductor components, and often additionally includes a specialized microprocessor and related chips. The card is also provided with a connector structure to interface with the host computer and, if appropriate, one or more connectors to interface with external communication means such as telephone lines. The card is typically encased in a two-part, light-gage stainless steel sheet metal housing.
Because the overall dimensions of a PCMCIA card are quite small, the generation of even a moderate amount of heat within the card can create excessive operating temperatures in the card. As a heat dissipating mechanism, convection is effectively negligible in the typical PCMCIA card operating environment where the card, upon operative insertion into the computer, is tightly surrounded by a card receiver, various connectors and assorted computer components, many of which are also heat-generating structures. Accordingly, PCMCIA card cooling must depend almost exclusively on conduction.
Current industry practice provides no special cooling features for PCMCIA cards. These cards may be used in larger computers such as desktops, in which case cooling is generally by forced convection and the cooling system in place for the computer may be adequate to cool any PCMCIA cards incorporated in the desktop computer. In smaller computers, however, the problem of cooling a PCMCIA card for reliability in a way that does not jeopardize the comfort of the user is not simple.
PCMCIA card cooling, in the past, has generally been approached by simply depending on conduction to spread the heat from the card into the remainder of the computer, and accepting the accompanying risk of uncomfortable product surface temperatures. The available conduction paths for dissipating operating heat from a PCMCIA card installed, for example, in a notebook computer include the PCMCIA card connector, the air within the card housing, and the air between the card housing and nearby, more conductive solid materials. Because air motion around the inserted card is effectively prevented by various physical structures closely surrounding it, the air immediately adjacent the inserted card acts substantially entirely as a conductive heat transfer medium and not a convective one.
None of these available heat conduction paths is suitably efficient from a heat transfer standpoint for dissipating operating heat from a PCMCIA card installed in a compact portable computer. It can thus be seen that a need exists for improved apparatus and methods for dissipating operating heat generated by a PCMCIA card installed in a portable computer, such as a notebook computer, or in other types of computers, such as desktop computers, where PCMCIA card cooling problems may arise. It is accordingly an object of the present invention to provide such improved apparatus and methods.